An inkjet recording device is used in a printer, a facsimile, a copier, and other image forming apparatuses. The inkjet recording device ejects ink drops from an ink recording head to a recording medium to record an image. The recording medium may be, for example, a piece of paper, an OHP sheet, or in general, a printing sheet, to which the drops of ink can adhere. The inkjet recording device is capable of recording fine images at high speed, has a low running cost and low noise. Further, by using multicolor ink, it is easy for the inkjet recording device to record color images.
In an inkjet recording device of the related art, a guide plate is provided opposite to an ink recording head, and the ink recording head prints onto a printing sheet when the printing sheet is conveyed onto the guide plate. Further, a spur having a projecting peripheral portion is also provided to press the printing sheet onto the guide plate during printing. By this structure, the printing sheet is kept flat during printing.
In the inkjet recording device of the related art, feeding of a printing sheet is performed by using two groups of rollers arranged one group at each end of a printing area. With this structure, however, it is difficult to obtain high feeding precision unless the printing sheet is firmly in contact to both of the groups of rollers.
For example, Japanese Laid Open Patent Application No. 2000-211768 discloses the above inkjet recording device of the related art.
Recently, a larger printing area has become required, and in order to increase the printing area, there is proposed an inkjet image recording device having only one group of rollers for feeding the printing sheet. But this device makes it even more difficult to obtain high feeding precision. Specifically, with the printing sheet being in contact to rollers at only one side, sometimes the printing sheet floats relative to the rollers sometimes, and a force for conveying the printing sheet cannot be obtained. Consequently, the feeding precision becomes low, and the image quality declines.
Therefore, inkjet recording devices are proposed to solve this problem in which, in order to maintain flatness of the printing sheet, a charged seamless belt is provided to hold the printing sheet on the belt by an electrostatic force due to the charge, and the belt is rolled in this state to convey the printing sheet. In this way, floating of the printing sheet from the belt is preventable and good flatness can be obtained.
For example, Japanese Laid Open Patent Application No. 7-53082, Japanese Patent Publication No. 2897960, and Japanese Laid Open Patent Application No. 5-518 disclose the above inkjet recording device.
Further, as disclosed in Japanese Laid Open Patent Application No. 7-53082, a guide plate is provided on the inner side of the seamless belt at a position corresponding to the printing area to improve flatness of the printing sheet.
In the inkjet recording device in which the printing sheet is fed while being held on the feeding belt by an electrostatic force, in order to stack the printing sheet on a sheet delivery unit, the printing sheet is separated from the feeding belt by curvature separation. However, relatively soft printing sheets cannot be easily separated from the belt. These printing sheets are continuously conveyed while being held on the belt, causing jams of the printing sheets.
In addition, in the above inkjet recording device of the related art, the feeding belt is tensioned by at least two rollers and the portion of the belt between the rollers corresponds to the printing area, that is, the area printed on by the inkjet head. This portion of the belt rumples easily, and oscillates in a direction perpendicular to the belt surface when the belt is rolled, causing declination of flatness of-the belt. Since generally the flatness of the printing sheet is directly related to flatness of the belt, the distance between the recording head and the printing sheet changes, causing image quality to decline.
In addition, even when a guide plate is provided in the way as described above, it is not easy to obtain high printing precision because the distance between the recording head and the printing sheet influences the printing precision and it is difficult to make the surface of the guide plate highly flat. Further, if the guide plate touches the moving charged seamless belt, the belt may lose the charge, and this lowers the electrostatic force for holding the printing sheet.